Method and apparatus for preventing venous blood clotting



April 20, 1965 P. A. MEREDITH 3,179,106

METHOD AND APPARATUS FOR PREVENTING VENOUS BLUOD CLOTTING Filed Sept.18, 1962 Q S 3 a o N .l E F. \\....35 t \9 I%IIII n W 7 5 INVENTOR: PAULA. MEREDITH Wei ATT'Ys United States Patent laul A. Meredith, 94d NorthEast Ave, Gals Park, llh

Filed Sept. 1S, 1962, Ser. No. 224,301 llClairns. (Qi. lid-=24) Thisinvention relates to a method and apparatus for preventingphlebothrombosis in the extremities andabdomen; more particularly, itinvolves the elimination of venous stasis in these body areas.

A primary cause of phlebothrombosis is venous stasis, typicallyresulting from inactivity, as with bed-ridden patients, or chroniccirculatory ailments. Phlebothrombosis is a particularly dangerouscondition in that the phlebothrombi often break up into emboli whichlodge in the lung, as they move toward the central portion of thecirculatory system. It is desirable to prevent phelbothrombosis as theconsequent risk of pulmonary embolism is substantially reduced. Thus,the principal object of this invention is to obtain a method for theprevention of phlebothrombosis in the extremities and abdomen.

Another object of the invention is to provide a method of the characterdescribed that will not interfere with normal circulation.

It is also an object to provide a device for preventing the formation ofphlebothrombi.

Yet another object is to provide a device of the charac ter describedthat will operate independently of patient cooperation.

Other objects and advantages of the invention will be apparent from thefollowing description in conjunction with the accompanying drawing inwhich:

FIGURE 1 illustrates a preferred embodiment of the invention;

FIGURE 2 illustrates diagrammatically a mechanism for intermittentlyproducing pulses of minimal pressure in practicing the embodiment ofFlGURE l; and

FIGURE 3 illustrates graphically the relationship between time andpressure according to one method of practicing the invention.

With these objects in view and other objects that will appear as thedescription proceeds, the method, broadly described, involves theremoval of static venous blood by intermittent application of minimalexternal pressure. The essence ofthe invention resides in to use ofrapid pulses of minimal pressure over prescribed intervals. In thenormal individual the. venous blood pressure is ap proximately 10millimeters of mercury (mm. Hg). In this novel method, intermittentapplication ofrapid pulses of external pressure of about this magnitudeis sufficient to empty static blood from the veins of the arms and legs.

Similarly, external pressure, applied intermittently in rapid pulses ofthe same approximate magnitude, will prevent stasis of blood in theabdominal veins. The great advantage of this method is that rapid pulsesof a minimal pressure do not interfere with circulation in thearterioles and capillaries, where the blood is under relatively higherpressure. This pulse of minimal pressure is strong enough to push theblood out of the vein, yet it is not so strong as to inhibit normalcirculation. Due to the short duration of the pulse, the veins rapidlyopen to permit influx of blood from more distant parts of thecirculatory system.

The pulse of minimal pressure is applied over a short period of time,from one-tenth to one second. In preferred form, the pulse has aduration of about one-half second. After the pulse is applied, therefollows a relatively longer idle period during which no pressure isapplied. This idle period is typically from 10 to 300 times the durationof the pulse of pressure. In the case of the preferred duration of thepulse of one-half second, the idle period would last from 5 to 150seconds. Varying "ice circumstances may make it necessary to apply thepressure pulse more or less often.

The magnitude of the pulse of pressure is quite small, barely beingperceptible to the patient. Typically, the pulse pressure is between 5and 15 mm. of Hg, being just suiiicient to overcome the normal venousblood pressure toempty the vein. In special cases, for example, withpatients having abnormally high venous blood pressures, thepulse'pressure may, of necessity, be as high as 30 mm. Hg.

The method of intermittently applying the rapid pulses of minimalpressure is equally effective in eliminating venous stasis in theextremities and in the abdomen. Thus, the pulses of minimal pressure,over the appropriate cycle,

ray be applied to any of the following parts of the body, as theindividual case demands: forearms, upperarms, calves, thighs andabdomen.

in a preferred embodiment of the invention, pulses of minimal pressureare applied in rapid sequence to different portions of the body. As anexample, a first pulse of minimal pressure to the calves and forearms, asecond pulse to the thighs and upperarms; and a third pulse to theabdomen. Following this there is the usual relatively longer periodduring which no pres no is exerted. This enrodiment of the method hasthe added advantage of systematically encouragingthe venous circulationin addi tion to the elimination of venous stasis and prevention ofphlebothrombosis.

This invention also provides a device for eficctuating the novel methodof preventing phlebothrombosis hereinefore described. In its most basicform, the device consists of pressure applying means, means forintermittently producing pulses of minimal pressure, connecting meansfor conveying the pulse of minimal pressure from the pressure producingmeans to the pressure applying means, and means for controlling thecycle of pulses and magnitude of the minimal pressure.

in preferred form the device provides a series of pressure applyingmeans whereby the pulses of minimal pressure can be applied in rapidsequence to different areas of the body. The series of pressure applyingmeans may be used in conjunction with a common pressure producingdevice, in which case distribution means must be provided whereby thepressure applying means will receive the pulses of minimal pressureselectively sequentially. Alternatively, each separate pressure applyingmeans, or con.- bination thereof may be provided with its own pressureproducing means. Control means are provided, in either embodimentwhereby the duration, cycle and magnitude of the sequence of pulses ofminimal pressure are regulated to conform to the individual patientsneeds.

The drawings illustrate one possible embodiment of this invention. FIG.1 shows this embodiment used on a bedridden patient. Referring to thenumbers, inflatable bladders 1 and 2, fashioned to fit the calves, and 3and 4, fashioned to fit the forearms are connected via hoses 5, 6, 7'and 8 and via connecting T 9 to a compression chamber 1t (FIG. 2) withinbox 11. Similarly, inflatable bladders 12 and 31, fashioned to fit thethighs, and 14 and 15, fashioned to fit the upper arms, are connectedvia hoses id, 17, 18 and 19 and via connecting T it) to a compressionmeans 21 within box ll. Hoses 5, d, '7 and 8 should be of relativelylarge cross section as the pressure increment is small. Inflatablebladder 2, fashioned to fitthe abdomen is connected via hose 23 andoutlet 24 to a compression means 25 within box ll. The box 11 contains,in addition to compression means 1t 21 and 25, cycle controlling means26, pressure regulating means 2'7 and gauges 28, 2s.

,FIUTJRE 2 shows schematically the interior to the box 11 of FIG. 1.Motor 3t? controlled byspeed control A is connected through drive wheel31 to shaft 32 via connecting rod 33. n shaft 32 are a series of cams36, 37, 3% adjustable for timing and displacement by adjusting screws36A, 37A and 38A. Compression means 10, 21 and 25 are formed of largecylinders 39, 40, 41 and diaphragms 42, 43, 44. Connecting tubes 48 and49 lead to connecting Ts 9 and 20 and connecting tube 59 leads to outlet24. Diaphragm rods 51, 52 and 53 press against shaft 32 and earns 36, 37and 33. Slide guides 34 control the path of movement of shaft 32 androds 51, 52, and

53. Not shown is a cam lifting mechanism at 34 to lift the cam rod 32off of the cam followers 51, 52 and 53 on the return stroke of the rod52. Springs 35 restore diaphragms 42, 43 and 44 to their initialpositions. Pressure equalizing valves 54, 55 and e are provided for eachof the cylinders 39, 40 and 41 to restore the initial air pressure toatmospheric after each actuation of the respective diaphragms. For thispurpose flipper valves or other self-equalizing valves can be used. Inthe absence of a pressure equalizing system, uniform action would not beobtained due to leakage of air which occurs to some extent in any closedsystem.

The operation of the device proceeds as follows: the motor 30 via drivewheel 31 and connecting rod 33 imparts reciprocating motion to shaft 32.Cams 36, 37 and 38 sequentially activate diaphragms 42, 43 and 44 viadiaphragm rods 51, 52 and 53. The diaphragm strokes, controlled by thesize and shape of the cams, are short and the movement of the diaphragmschanges only slightly the volume of the cylinder. The minimal pressure,se-

quentially produced in the cylinders 39, 4t and 41 is conveyed via tubes48, 49 and 50, via connecting Ts 9 and 2t) and outlet 24 and via hoses5, 6, 7, 8, 116, 17 18, 19 and 23 to inflatable bladers, ll, 2, 3, 4,12, 13, 14, and 22. The initial order is A, B, C, i.e., lower legs,lower arms (A), upper legs, upper arms (B) and abdomen (C). Thediaphragm compression cylinders are of such size that the diaphragmstrokes will cause only a small reduction in the total volume of thesystem (i.e., cylinder plus bladders) and will produce a minimalsuperatmospheric pressure of about 5 to 15 millimeters of mercury in thesystem.

FIG. 3 is a graphical depiction of the sequence of pulses produced bythe embodiment of FIGS. 1 and 2. It is a plot of pressure, in mm. Hgversus time. Curve 57 shows the pressure-time relationshipcharacteristic of compression means It), curves 58 and E9 show similarrelationships for compression means 21 and which are activatedsequentially thereafter.

There is next a relatively longer period of time during which nopressure is exerted, whereupon the cycle of three sequentially producedpulses is repeated (curves 60, 61 and 62).

While one preferred embodiment of the device is shown, it is obviousthat many changes can be made without departing from the spirit of theinvention. The number of sequential cycles can be varied, for example,from one to ten.

The pressure cylinders are preferably capable of holding rather largevolumes of fluid such as air, e.g., 25 liters, and the reduction ofvolume is preferably minor, e.g., 5% or less, as compared to the totalvolume of the cylinders.

The inflatable bladders are made of rubber or any other expandable,inflatable material which can, if desired, be covered with cloth. Thesebladders are generally similar in construction to those used by themedical profession for application to the arms for blood pressuredeterminations.

The invention is hereby claimed as follows:

1. The method for preventing blood clot formation in the veins of theextremities and abdomen which comprises intermittently'emptying theblood from said veins by the application of minimal external pressure tosaid body member just suflicient to overcome the normal venous bloodpressure and to empty the veins, said minimal pressure being at leastabout 5 millimeters of mercury and not 4 exceeding about 30 millimetersof mercury and being exerted in rapid pulses and said pulses beingfollowed by a relatively longer idle period during which no pressure isexerted.

2. The method for preventing blood clot formation in the veins of theextremities and abdomen which comprises intermittently emptying theblood from said veins by the application of minimal external pressure ofabout 5 to 15 millimeters of mercury to said body members, said minimalpressure being exerted in rapid pulses, said pulses being followed by arelatively longer idle period during which no pressure is exerted.

3. The method for preventing blood clot formation in the veins of theextremities and abdomen which comprises intermittently emptying theblood from said veins by the application of minimal external pressure tosaid body members, said minimal pressure being exerted in a sequence ofrapid pulses not exceeding about one second in duration, said sequenceof pulses being followed by a relatively longer idle period during whichno pressure is exerted, the magnitude of said minimal pressure beingabout 5-15 millimeters of mercury.

4. The method for preventing blood clot formation in the veins of theextremities and abdomen which comprises intermittently emptying theblood from said veins by the application of minimal external pressure ofabout 5 to 15 millimeters of mercury to said body members, said minimalpressure being applied in a sequence of rapid pulses, said pulses beingfollowed by a relatively longer idle period during which no pressure isexerted, each of the pulses of said sequence lasting about one-halfsecond and said idle period lasting from about 5 to seconds.

5. The method for preventing blood clot formation in the veins of theextremities and abdomen which comprises intermittently emptying theblood from said veins by the application of minimal external pressure tosaid body members, said minimal pressure being applied in a sequence ofthree rapid pulses, the first pulse being applied to the calves andforearms, the second to the thigh and upperarms, and the third to theabdomen, said sequence of three pulses being followed by a relativelylonger idle period during which no pressure is exerted, said minimalpressure being about 5-15 millimeters of mercury, said sequence ofpulses lasting no longer than about three seconds and said idle periodlasting from about 10 to 300 times longer than said sequence of pulses.

6. An apparatus for preventing blood clot formation in the veins of theextremities and abdomen comprising means for applying pulses of minimalpressure to the extremities and abdomen, means for producing said pulsesof minimal pressure of at least about 5 millimeters of mercury and notexceeding about 30 millimeters of mercury, means for connecting saidapplying means and said producing means, means for controlling themagnitude of the minimal pressure developed in said pressure producingmeans and means for regulating the operation cycle of said producing andsaid applying means whereby each of said pulses of minimal pressure isproduced and applied rapidly followed by a relatively longer idle periodduring which no pressure is exerted.

7. An apparatus for preventing blood clot formation in the veins of theextremities and abdomen comprising means for applying pulses of minimalpressure to the extremities and abdomen, means for producing pulses ofminimal pressure of about 5 to 15 millimeters of mercury, means forconnecting said applying means and said producing means, means forregulating the magnitude of the minimal pressure produced and means forregulating the operation cycle of said applying means and said producingmeans whereby said pulses of minimal pressure are produced and appliedrapidly followed by a relatively longer idle period during which nopressure is exerted and whereby a pulse of said minimal pressure lastsno longer than about 1 second and said idle period lasts from about 5 toabout 150 seconds.

8. An apparatus for preventing blood clot formation in the veins of theextremities and abdomen comprising a series of means for applying rapidpulses of minimal pressure to the extremities and abdomen, means forproducing said pulses of minimal pressure, the magnitude of said pulsesbeing about 5-15 millimeters of mercury, means for regulating themagnitude of the minimal pressure produced, means for distributing saidpulses of minimal pressure whereby said series of applying meanssequentially receive said pulses of minimal pressure, each one of saidpulses lasting no longer than about 1 second, and whereby the sequentialdistribution of said pulses is followed by a relatively longer idleperiod during which no pressure is exerted, said idle period lastingfrom about to 300 times longer than one of said rapid pulses.

9. An apparatus for preventing blood clot formation in the veins of theextremities and abdomen comprising a series of similarly constructedpressure systems each comprising means for applying rapid pulses ofminimal pressure to the extremities and abdomen, means for producingsaid pulses, the magnitude of said pulses being at least about 5millimeters and not exceeding about 30 millimeters of mercury, means forconnecting said producing means and said applying means, means forregulating the magnitude of said pulses, means for regulating theoperation cycle of said series of pressure systems whereby said pulsesare rapidly and sequentially produced and applied followed by arelatively longer idle period during which no pressure is exerted.

10. An apparatus for preventing blood clot formation in the veins of theextremities and abdomen comprising a series of similar pressure systemseach comprising inflatable bladders adapted to fit a body member, eachsystern comprising a diaphragm type compression cylinder of suchsizethat the diaphragm stroke will cause only a small reduction in thetotal volume of the cylinder and bladders and will produce a minimalsuperatmospheric pressure at least about 5 millimeters and not exceedingabout 30 millimeters of mercury in the system, said cylinder beingprovided with an equalization valve suitable for returning the system toatmospheric pressure after said diaphragm stroke is completed; hosesconnecting said cylinder and said bladders; a cam connected to activatethe diaphragm of each of said systems; motor means driving said cams;means for regulating the magnitude of the pulses of minimal pressureproduced in said systems; and means for regulating the operation cycleof said systerns whereby said series of systems is activated rapidly andsequentially by said motor driven cam followed by a relatively longeridle period during which no pressure is produced or applied.

11. The apparatus of claim 10 wherein. there are three of said pressuresystems, the first having four of said bladders, two adapted to fit thecalf and two adapted to fit the forearms, the second of said systemshaving four of said bladders, two adapted to fit the thigh and twoadapted to fit the upper arms, and the third of said systems having onesaid bladder adapted to fit the abdomen.

References Cited in the file of this patent UNITED STATES PATENTS2,361,242 Rosett Oct. 24, 1944 2,959,171 Seligman NOV. 8, 1960 RICHARDA. GAUDET, Primary Examiner. RICHARD. J. HOFFMAN, Examiner.

1. THE METHOD FOR PREVENTING BLOOD CLOT FORMATION IN THE VEINS OF THEEXTREMITIES AND ABDOMEN WHICH COMPRISES INTERMITTENTLY OF MINIMALEXTERNAL PRESSURE TO SAID BODY APPLICATION OF MINIMAL EXTERNAL PRESSURETO SAID BODY MEMBER JUST SUFFICIENT TO OVERCOME THE NORMAL VENOUS BLOODPRESSURE AND TO EMPTY THE VEINS, SAID MINIMAL PRESSURE BEING AT LEASTABOUT 5 MILLIMETERS OF MERCURY AND BEING EXCEEDING ABOUT 30 MILLIMETERSOF MERCURY AND BEING EXERTED IN RAPID PULSES AND SAID PULSES BEINGFOLLOWED BY A RELATIVELY LONGER IDLE PERIOD DURING WHICH NO PRESSURE ISEXERTED.